Technical Abstract:
Stress can lead to changes in the immune response of turkeys resulting in decreased resistance to opportunistic bacterial pathogens. Three lines of turkeys were tested for response in T-maze and open field tests during the first 8 days after hatch and behavior was observed after catching, moving, and transport. They were also compared for corticosterone (Cort) levels and heterophil/lymphocyte ratios (H/L) at 15 wk of age, in response to an Escherichia coli challenge followed by transport stress. Large commercial line birds (Comm) were faster and more active in the T maze at day 2 than smaller Egg line birds. Male Comm line birds were faster than male Egg line birds when tested in an open field at day 8. Egg line birds had more sleeping behavior after moving to a new floor pen as compared to both an intermediate-sized line (F line) and the Comm line. Transport stress increased Cort levels in all 3 lines and the increase was greater in males compared to females. The Egg line had higher basal Cort levels (P = 0.03) and higher levels after transport (P< 0.0001). The H/L ratios were affected by both transport stress and line but not by sex. The H/L ratio was lower in the Egg line as compared to both the F line and the Comm line (P< 0.0001), with the Comm line having the greatest increase in response to transport. Previous studies determined that Egg line birds were more resistant to the deleterious effects of challenge and the Comm line displayed the most adverse effects. These data suggest that differences in activity of fast-growing turkeys may be used to select birds that are less susceptible to inflammatory bacterial disease and that the H/L ratio may be more useful than serum Cort in evaluating the deleterious effects of stress.